Aggregate of cells and intercellular substances specialized to perform a particular function

While the size of a band changes during contraction and relaxtion does the actin and myosin length itself?

No

What colour is the I band? A band?

I = light

A = dark

What are 4 basic tissues?

Epithelium

Connective

Muscle

Nerves

A cyte is a _____ cell? While a blast is a _____ cell?

Mature

Immature

In skeletal muscle where do we find th enucleus almost always? Why?

On the edge of the fiber

Cause all th ebands push it there

What is a satellite cell?

sits in basement membrane essentially undifferentiated stem cell, can add nuclei to the muscle fibers and make it grow

When you excersise do your muscles grow or do you get more of them?

They grow

Describe hypertrophy in muscle cells?

Increase in size

What is a myofibril?

Bundle of actin and myosin within a cell

Differentiate between a myofibre and myofibril

Fibre is cell fibril is within a cell

Define endomysium, epimyisum, and perimysium

Endo = inbetween individual cells

Peri = inbetween bundles

Epi = on outside of muscle

Are the bands in a muscle all lined up generally evenly? Like A to A and I to I?

Yes usually to an extent

Holes on surface of the sarcolemma leading to tubes used to conduct electricity are called?

T tubules

Why do T tubules make sense for skeletal muscle

Generally we want the entire muscle fibre to contract at once the myofibrils on the inside and outside so the T tubules allow penetration through the entire cell and allow the AP to stimulate everything

Generally in other kinds of muscle this perfect timing is not so important

Plasma membrane in muscles is the ? What about smooth ER?

Sarcolemma

Sarcoplasmic reticulum

What band disappears during contraction (or can)?

H band

What is a motor unit?

A group of fibers to be contracted at once, 1 nerve for tonnes of fibers

What is the thin filament?

Actin

What covers the binding sites on actin?

Tropomyosin

What pulls the troponin complex off of the actin?

Ca

The tail of myosin is made of what?

2 heavy chais twisted around eachother

is myosin directly anchored itself to the Z line? What about actin?

No only through titin

Yes

A sarcomere is measured from?

Z line to Z line

Why do we see bands in the first place? What band is within the A band? What line is within that?

Cause different proteins make up different bands

H band

M line

which fiber type (red/white) is faster? Uses mor Oxygen? has more mitochondria? is anaerobic primarily?

White

Red

Red

White

What is the purpose of a muscle spindle?

TO gauge the tension on the muscle

Do skeletal muscles have gap junctions?

Nope they are all one cell why would they need it

In cardiac muscles what connects cells

Intercallated discs

Are cardiac muscle cells as long and connected as skeletal?

No they are short and autonomous

Are cardiac muscles controlle dby the brain at all?

No they are purely autonomous

How is myofilament shape in cardiac muscles? do we see striations and the same movement?

Yes it is it the exact same and you get the same movement however the shape of the cell is not the same

on a transverse cut through thecardiac muscle we happened to cut right through a nucleus and it appeard as a black dot surrounded by an empty space? What is the space for?

Storage space for glycogen and lipids

Where would we expect to see more mitochondria in cardiac muscle or smooth muscle?

Cardiac muscle cause it runs contantly and is unyielding can see as much as 20-40% of cytoplasm as mitochondria

Do we see the same level of SR in the cardiac muscle?

No it is less developed which means that we don't rely on it as much and T tubule does more Ca release

Name 4 differences between skeletal and cardiac muscle

Cardiac is not one giant long multi nucleated cell, a lot more mitochondria, not as developed SR, autonomous

Do we still the banding pattern in muscles when O 2 is lost?

No and they contract in a funny way

Myocardial infarction?

Heart attack

How many arteries does the heart have? How does gthis compare to other important organs? Describe the relevance to myocardial infarction

1

low

If it gets plugged with plaque you die

in the intercalated dsics of cardiac muscle cells what are some things we find? What do these look like?

desmosomes

gap junctions on the vertical part that done support any tension

Spot welds (des) and discs (gap junctions)

describe how the muscle cells in the heart communicate and how this gives a very rhythmic contaction profile of it

They are not all connected and so there is a lag while they communicate vetween the gap junctions this means cell #2 contracts some time after Cell #1 after this lag occurs causing a drawn out squezzing effect

if all the muscles contracted at once in the atrial the blood would go no where

Cardiac impulse conducting fibers are also known as?

Purkinje fibers

Purkinje fibers fire because of what?

They are very leaky and so spontaneously fire at a base frequency

Where do purkinje fibers originate?

Nodes such as the AV or Sa node

Histologically what do purkinje fibers look like?

A lot larger in cross diameter than cardiac muscles

How does the action potential spread through cardiac muscle?

Through the gap junctions to the next cell

This causes orderly and sequential contraction

Do cardiac muscles have satellite cells?

Essentially no

Can the heart beat without the brain?

Yes it is autanomous

What determines the strength of a contraction in skeletal muscle as compared to cardiac muscle?

Skeletal muscle it is the number of fibers contracting but all fibers go full force

In cardiac muscle it is the extent the cells contract but they all contract

Is the cardiac muscle able to divide at animal maturation?

No the ability to divide is lost after birth

How does the heart grow?

Heart grows cause cells and individual fibres grow

Damage to the heart wall (infarction leads to death of myocytes. What usually fills this gap?

Connective tissue proliferation

How does smooth muscle appear? Does it have any striations? Why does it appear smooth?

Smooth and silky

No

Cause actin and myosin are not in any definitive arrangement like in the other muscles and therefore don't make a pattern

Which muscle type is the most efficient and has the highest amount of contracting power

Smooth muscle

What is the shape of a smooth muscle cell and what is the shape of the nucleus

Cigar shaped nucleus and a spindle shaped cell

What interconnects muscle fibers?

Collagen

In the intestines how many layers of muscle are there?

2

Do all visceral orgajns have smooth muscle?

Yes to an extent

Does each smooth muscle need its own nerve?

No one nerve kind of dumps out and many muscle cells pick it up

Do Smooth muscles have T tubules?

No they lack that entire system they have vesicles that take in Ca and the contraction mechanism is completely different

What are dense bodies?

They are places where both actin and intermediate filamnents in smooth muscle attach to both in the cytosol and on the plasmalemma it is there anchor per say

What is a third type of filament smooth muscle cells have?

Intermediate filaments made of desmin

Smooth muscle is a very efficient contractor, describe what we see in a smooth muscles appearanbce when it contracts

It contracts so much that is essentially bundles up and kinks

What do we call a neuromuscular synapse in a muscle?

A motor end plate

What is the difference in muscle spindles in smooth muscle?

They are very prominent so w e often study them here

Describe what is inside a muscle spindle?

Modified skeletal muscles much smaller with a capsule surrounding it

Sensory nerves within it detect how much muscle is being contracted and makes the brain think about the tension